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This article explains how sound energy is transferred through waves. It covers topics such as the movement of air particles, compression and rarefaction, mediums through which sound can travel, loudness and its factors, pitch and its dependence on frequency, and how to change pitch in singing and with musical instruments.
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Learning Target 2 Describe how sound energy is transferred by waves.
How do sound waves travel through the air? The vibrations disturb nearby air particles. Each time the gong moves to the right, it pushes air particles together, creating a compression. When the gong moves to the left, the air particles bounce back and spread out, creating a rarefaction. These compressions and rarefactions travel through the air as longitudinal waves.
What is Sound? Sound is a disturbance that travels through a medium as a longitudinal wave.
How does a sound wave begin? A sound wave begins with a vibration.
What mediums can sound travel through? A common medium for sound is air, but sound can travel through solids and liquids, too.
What is Loudness? Describes your perception of the energy of a sound. In other words, loudness describes what you hear. https://www.youtube.com/watch?v=CewacsP6TSY
What does loudness depend on? The loudness of a sound depends on two factors: the amount of energy it takes to make the sound and the distance from the source of the sound.
How does energy affect the loudness of the sound? In general, the greater the energy used to make a sound, the louder the sound. The more energy you used to pull the guitar string back, the louder the sound when you let the string go. This happened because the more energy you used to pull the string, the greater the amplitude of the string’s vibration. A string vibrating with a large amplitude produces a sound wave with a large amplitude. Recall that the greater the amplitude of a wave, the more energy the wave has.
How does distance affect the loudness of the sound? Loudness increases the closer you are to a sound source. Imagine ripples spreading out in circles after you toss a pebble into a pond. In a similar way, a sound wave spreads out from its source. Close to the sound source, the sound wave covers a small area. As the wave travels away from its source, it covers more area. The total energy of the wave, however, stays the same. So same energy in a larger area equals a lower intensity or more quiet sound.
How is loudness measured? The amount of energy a sound wave carries per second through a unit area is its intensity. The loudness of different sounds is compared using a unit called the decibel (db)
What is pitch? The Pitch of a sound is a description (perception) of how high or low the sound seems to a person
What does pitch depend on? The pitch of a sound that you hear depends on the frequency of the sound wave.
How do you change pitch when you sing? To sing different notes, you use muscles in your throat to stretch and relax your vocal cords. When your vocal cords stretch, they vibrate more quickly as the air rushes by them. This creates higher-frequency sound waves that have higher pitches. When your vocal cords relax, lower-frequency sound waves with lower pitches are produced. With musical instruments, you change pitch in different ways depending on the instrument. For example, you can change the pitch of a guitar string by turning a knob to loosen or tighten the string. A tighter guitar string produces a higher frequency, which you hear as a note with higher pitch.
http://www.youtube.com/watch?v=irqfGYD2UKw&feature=player_detailpagehttp://www.youtube.com/watch?v=irqfGYD2UKw&feature=player_detailpage
Learning Target 2 Describe how sound energy is transferred by waves.
